The isolation and characterization of insulin and glucagon receptors from the plasma membranes of rat liver and epididymal fat pads is being carried out. Experiments are being carried out to determine the rates of synthesis and degradation of these receptors. Studies will also be carried out to determine if nutritional or hormonal factors modify the turnover rate. Methods have been developed for the measurement of the activity of glycerophosphate acyl-transferase and phosphatidic phosphohydrolase. Experiments characterizing these enzymes with regard to their physical and kinetic properties will be carried out. The methods for the measurement of the activities of these enzymes will be employed to determine the effects of feeding, fasting, and insulin and other hormones on triglyceride synthesis.